So, the phone was instantly recognized as a modem and we were able to get onto the Internet. Combined with a laptop, this could be very useful for sending and receiving emails when no landline is available.
The printer connection was no problem either. In fact, it was the quickest and most satisfactory test we ran. The printer was detected in a dozen seconds and installed in another 30, after which we could all share the Deskjet 450 via Bluetooth from the master computer. The output rate did not suffer at all: it was still 2.6 pages per minute in color and black and white, and about three minutes for a 10x15 cm photo at 300 dpi. The asynchronous rate is therefore perfectly adequate, even for hefty files (the test photo weighed 5.62 MB). This means one less cable for a desktop computer, but for a laptop the gain is even better.
In addition, the performance of the keyboard and mouse was not at all affected by the simultaneous phone connection to the Internet or the printer. So it can handle four activities at once.